The present invention relates to semiconductor product packaging and methods of fabrication for producing a packaged semiconductor product. More particularly, the present invention relates to leadless semiconductor product packaging and methods of fabrication for producing leadless packaged semiconductor product. Even more particularly, the present invention relates to leadless semiconductor product packaging and methods of fabrication for mass-producing packaged semiconductor product without employing time-consuming, environmentally-unfriendly related art lead-frame etching and de-flashing techniques.
In response to manufacturing cost concerns relating to populating printed circuit boards with electronic product having the requisite functional circuits, the semiconductor product packaging industry has developed a leadless circuit component product (also known as a surface mountable electronic product), hereinafter referred to as a xe2x80x9cleadless product.xe2x80x9d The leadless product, as the name implies, is a packaged electronic product that does not require the use of physical leads for being inserted into mating holes provided on a planar board as a mechanical mounting means nor as an electrical connection with other electronic components forming the circuit on such a planar board. In general, the leadless product facilitates manufacturing of a printed circuit card, thereby eliminating the inserting of component leads into the board holes and the soldering of these leads to the board""s solder pads. The leadless technology has been well accepted as an option for packaging electronic components since early 1980. By example, a current related art industrial product includes xe2x80x9cQFNxe2x80x9d (Quad Flat No Lead, registered as JEDEC STD MO 197, 198, 208, 209, and 220). Of course, the electronic component function may still be available in a lead-type packaging structure.
In the related leadless semiconductor product packaging art, xe2x80x9chalf-etchingxe2x80x9d techniques are used for forming the lead-frame, generating considerable hazardous material (e.g., acid waste, metals waste, and possibly organic solvent waste); and an adhesive tape is used to temporarily mask effective solderable areas of the lead-frame (also known as the xe2x80x9couter I/Oxe2x80x9d) from the packaging material to be applied during the molding process in order to preserve such effective solderable areas of the lead-frame in an un-insulated state, generating undue tape and possibly organic solvent waste. In another related semiconductor product packaging art technique, the lead-frame is completely packaged by a molding process; and the effective solderable areas of the lead-frame must be subsequently xe2x80x9cde-flashedxe2x80x9d in a process wherein such portions are blasted with a highly pressurized aqueous slurry of particulates (i.e., wet-blasting) to remove the xe2x80x9cover-packaging,xe2x80x9d thereby generating considerable hazardous material in the form of polymeric waste slurry. Therefore, a need exists for providing a natural resource-conservative and environmentally-friendly method and apparatus for packaging a leadless semiconductor product.
The present invention, a leadless semiconductor packaging apparatus, provides a cost-effective product, having superior mechanical, electrical, and thermal properties, and having an optional window lid feature (i.e., a sight lid) which not only uniquely seals, but also provides a mechanism for viewing the internally packaged integrated semiconductor circuits (chips/die). Cost reduction is achieved by (a) optionally using polymeric materials, such as epoxies, rather than conventional related art ceramic materials for packaging devices, and (b) simplifying the packaging process, thereby improving productivity.
The present invention employs a unique xe2x80x9cstampedxe2x80x9d and/or xe2x80x9cbentxe2x80x9d standard solder-plated or pre-plated lead-frame which is packaged by a polymeric material during a molding process, in contrast to the related art xe2x80x9chalf-etchedxe2x80x9d lead-frame. The process of the present invention involves providing a unique compression-type mold, specially contoured to avoid xe2x80x9cover-packaging,xe2x80x9d of the effective solderable areas of the lead-frame which is a common problem in the related art techniques. Applicants"" invention results in streamlining the device fabrication and packaging process. The specially contoured compression-mold facilitates delineation of the internal portions from the external portions of the lead-frame, where the external portions have the effective solderable areas that contact pads on a printed circuit board. The mold effectively provides a xe2x80x9ccompressive sealing orificexe2x80x9d from which the effective solderable areas of the lead-frame may extend and be exposed and, thus, avoid being coated with the polymer which is contained by the mold for packaging the internal portions of the lead-frame, thereby avoiding a laborious masking step and a tedious de-flashing step.
The present invention applies the unique technique of xe2x80x9cstampingxe2x80x9d and/or xe2x80x9cbendingxe2x80x9d of the lead-frame, thereby conforming it to electro-mechanical requirements of a particular semiconductor product. By stamping and/or bending the lead-frame material into the desired configuration, the present invention does not require old art xe2x80x9chalf-etchingxe2x80x9d of the lead for conforming it to electro-mechanical requirements of the packaged semiconductor product. By example, the related art process xe2x80x9chalf-etchesxe2x80x9d the lead-frame (e.g., 10 mils of raw conducting material are etched to about 5 mils, thereby generating a large volume of acid and conducting material hazardous waste) in order to create the requisite shape. Thus, thinner lead-frame material, such as that in a range of 6 mils or less, may be used with the present invention. The present invention offers several more distinctive advantages: (a) customer-specifiable package size, (b) applicable existing surface mount technology (SMT) processes, (c) overall improved performance at a lower cost, (d) complete absence of hazardous material by-products in full-scale production (environmentally-friendly, i.e., no acid waste, no metals waste, no liberation of volatile organic compounds, and no solid polymeric slurry waste), and (e) thinner lead-frame material (natural-resource-conservative).